```html
<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>深入理解JVM CMS垃圾收集器中的浮动垃圾问题</title>
    <link href="https://cdn.staticfile.org/font-awesome/6.4.0/css/all.min.css" rel="stylesheet">
    <link href="https://cdn.staticfile.org/tailwindcss/2.2.19/tailwind.min.css" rel="stylesheet">
    <link href="https://fonts.googleapis.com/css2?family=Noto+Serif+SC:wght@400;500;600;700&family=Noto+Sans+SC:wght@300;400;500;700&display=swap" rel="stylesheet">
    <style>
        body {
            font-family: 'Noto Sans SC', 'Noto Serif SC', Tahoma, Arial, Roboto, "Droid Sans", "Helvetica Neue", "Droid Sans Fallback", "Heiti SC", "Hiragino Sans GB", Simsun, sans-serif;
            line-height: 1.8;
            color: #333;
            background-color: #f9fafb;
        }
        .hero-gradient {
            background: linear-gradient(135deg, #4f46e5 0%, #7c3aed 50%, #9333ea 100%);
        }
        .content-card {
            transition: transform 0.3s ease, box-shadow 0.3s ease;
        }
        .content-card:hover {
            transform: translateY(-5px);
            box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
        }
        .section-divider {
            height: 2px;
            background: linear-gradient(90deg, rgba(79,70,229,0.1) 0%, rgba(124,58,237,0.5) 50%, rgba(79,70,229,0.1) 100%);
            margin: 3rem 0;
        }
        .drop-cap::first-letter {
            float: left;
            font-size: 3.5rem;
            line-height: 1;
            margin: 0.2em 0.1em 0 0;
            color: #4f46e5;
            font-weight: bold;
        }
        .highlight-box {
            border-left: 4px solid #4f46e5;
            background-color: rgba(79,70,229,0.05);
        }
        .timeline-item:before {
            content: '';
            position: absolute;
            left: -1.5rem;
            top: 0;
            width: 12px;
            height: 12px;
            border-radius: 50%;
            background-color: #4f46e5;
            border: 3px solid rgba(79,70,229,0.2);
        }
        .timeline-connector {
            position: absolute;
            left: -1.25rem;
            top: 12px;
            bottom: -1.5rem;
            width: 2px;
            background-color: rgba(79,70,229,0.2);
        }
    </style>
</head>
<body class="antialiased">
    <!-- Hero Section -->
    <section class="hero-gradient text-white py-16 md:py-24 px-4">
        <div class="max-w-5xl mx-auto">
            <div class="flex flex-col md:flex-row items-center">
                <div class="md:w-2/3 md:pr-10">
                    <h1 class="text-4xl md:text-5xl font-bold mb-4 leading-tight">深入理解JVM CMS垃圾收集器中的<span class="text-indigo-200">浮动垃圾</span>问题</h1>
                    <p class="text-xl md:text-2xl text-indigo-100 mb-8">探究并发标记清除机制下的内存管理挑战与优化策略</p>
                    <div class="flex flex-wrap gap-3">
                        <span class="px-3 py-1 bg-indigo-700 bg-opacity-50 rounded-full text-sm font-medium">#JVM</span>
                        <span class="px-3 py-1 bg-indigo-700 bg-opacity-50 rounded-full text-sm font-medium">#垃圾回收</span>
                        <span class="px-3 py-1 bg-indigo-700 bg-opacity-50 rounded-full text-sm font-medium">#CMS</span>
                        <span class="px-3 py-1 bg-indigo-700 bg-opacity-50 rounded-full text-sm font-medium">#性能优化</span>
                    </div>
                </div>
                <div class="md:w-1/3 mt-8 md:mt-0 flex justify-center">
                    <div class="bg-white bg-opacity-10 p-6 rounded-2xl backdrop-blur-sm border border-white border-opacity-20 shadow-lg">
                        <div class="text-center">
                            <i class="fas fa-microchip text-5xl text-indigo-200 mb-4"></i>
                            <h3 class="font-bold text-xl mb-2">关键概念</h3>
                            <p class="text-indigo-100 text-sm">CMS (Concurrent Mark-Sweep) 是一种面向低停顿的垃圾收集器，旨在减少GC停顿时间</p>
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </section>

    <!-- Main Content -->
    <main class="max-w-5xl mx-auto px-4 py-12">
        <!-- Introduction -->
        <section class="mb-16">
            <div class="content-card bg-white rounded-xl shadow-md p-8">
                <p class="drop-cap text-gray-700 mb-6">在 Java 虚拟机 (JVM) 中，CMS (Concurrent Mark-Sweep) 是一种面向低停顿的垃圾收集器，其设计目的是在应用运行时尽量减少垃圾收集的停顿时间，以提升应用的响应性。然而，由于 CMS 的并发清理机制，会产生一种被称为"浮动垃圾"(Floating Garbage)的现象，这也是 CMS 垃圾收集器的一个特性和难题。</p>
                
                <div class="highlight-box p-5 rounded-lg mb-6">
                    <div class="flex items-start">
                        <div class="flex-shrink-0 text-indigo-500 mr-3 mt-1">
                            <i class="fas fa-info-circle text-xl"></i>
                        </div>
                        <div>
                            <h4 class="font-bold text-gray-800 mb-1">什么是浮动垃圾？</h4>
                            <p class="text-gray-700">浮动垃圾是在CMS清理阶段由于垃圾收集与应用程序并发运行所产生的临时不可达对象。这些对象已经被标记为存活，但实际上应用已经不再引用它们。</p>
                        </div>
                    </div>
                </div>
            </div>
        </section>

        <!-- Section 1 -->
        <section class="mb-16">
            <div class="flex items-center mb-8">
                <div class="bg-indigo-100 w-12 h-12 rounded-full flex items-center justify-center mr-4">
                    <span class="text-indigo-600 text-xl font-bold">1</span>
                </div>
                <h2 class="text-3xl font-bold text-gray-800">CMS 垃圾收集器的工作机制</h2>
            </div>
            
            <div class="content-card bg-white rounded-xl shadow-md p-8 mb-8">
                <p class="text-gray-700 mb-6">CMS 垃圾收集器采用的是"标记-清除"算法，执行流程主要分为以下几个阶段：</p>
                
                <div class="relative max-w-4xl mx-auto">
                    <div class="timeline-item relative pl-8 pb-8">
                        <div class="timeline-connector"></div>
                        <h3 class="text-xl font-bold text-indigo-700 mb-2">初始标记 (Initial Mark)</h3>
                        <p class="text-gray-700">短暂停顿，标记 GC Roots 直接引用的对象。</p>
                    </div>
                    
                    <div class="timeline-item relative pl-8 pb-8">
                        <div class="timeline-connector"></div>
                        <h3 class="text-xl font-bold text-indigo-700 mb-2">并发标记 (Concurrent Mark)</h3>
                        <p class="text-gray-700">在应用线程并发运行的情况下标记可达对象。</p>
                    </div>
                    
                    <div class="timeline-item relative pl-8 pb-8">
                        <div class="timeline-connector"></div>
                        <h3 class="text-xl font-bold text-indigo-700 mb-2">重新标记 (Remark)</h3>
                        <p class="text-gray-700">短暂停顿，标记在并发标记阶段后存活的对象，确保引用链的完整性。</p>
                    </div>
                    
                    <div class="timeline-item relative pl-8">
                        <h3 class="text-xl font-bold text-indigo-700 mb-2">并发清除 (Concurrent Sweep)</h3>
                        <p class="text-gray-700">与应用线程并发运行，清除标记阶段判定为不可达的对象。</p>
                    </div>
                </div>
                
                <div class="mt-8">
                    <p class="text-gray-700">其中，并发标记和并发清除阶段都是和应用程序线程并行运行的，这意味着在 CMS 垃圾收集器执行清除时，应用程序仍然可以创建新对象。这些新创建的对象可能在 CMS 的清除阶段被视为垃圾，但在应用线程继续运行的过程中，实际已经不再被引用了。这些对象即为"浮动垃圾"。</p>
                </div>
            </div>
            
            <div class="grid md:grid-cols-2 gap-6">
                <div class="content-card bg-white rounded-xl shadow-md p-6">
                    <div class="flex items-center mb-4">
                        <div class="bg-indigo-100 w-10 h-10 rounded-full flex items-center justify-center mr-3">
                            <i class="fas fa-check text-indigo-600"></i>
                        </div>
                        <h3 class="font-bold text-lg text-gray-800">CMS的优势</h3>
                    </div>
                    <ul class="text-gray-700 space-y-2">
                        <li class="flex items-start">
                            <i class="fas fa-check-circle text-indigo-500 mr-2 mt-1"></i>
                            <span>减少GC停顿时间，提高应用响应性</span>
                        </li>
                        <li class="flex items-start">
                            <i class="fas fa-check-circle text-indigo-500 mr-2 mt-1"></i>
                            <span>并发执行垃圾回收，降低对应用线程的影响</span>
                        </li>
                        <li class="flex items-start">
                            <i class="fas fa-check-circle text-indigo-500 mr-2 mt-1"></i>
                            <span>适合对延迟敏感的应用场景</span>
                        </li>
                    </ul>
                </div>
                
                <div class="content-card bg-white rounded-xl shadow-md p-6">
                    <div class="flex items-center mb-4">
                        <div class="bg-red-100 w-10 h-10 rounded-full flex items-center justify-center mr-3">
                            <i class="fas fa-exclamation-triangle text-red-600"></i>
                        </div>
                        <h3 class="font-bold text-lg text-gray-800">CMS的局限</h3>
                    </div>
                    <ul class="text-gray-700 space-y-2">
                        <li class="flex items-start">
                            <i class="fas fa-times-circle text-red-500 mr-2 mt-1"></i>
                            <span>会产生浮动垃圾问题</span>
                        </li>
                        <li class="flex items-start">
                            <i class="fas fa-times-circle text-red-500 mr-2 mt-1"></i>
                            <span>对CPU资源敏感，并发阶段会占用计算资源</span>
                        </li>
                        <li class="flex items-start">
                            <i class="fas fa-times-circle text-red-500 mr-2 mt-1"></i>
                            <span>无法处理内存碎片问题</span>
                        </li>
                    </ul>
                </div>
            </div>
        </section>

        <!-- Section Divider -->
        <div class="section-divider"></div>

        <!-- Section 2 -->
        <section class="mb-16">
            <div class="flex items-center mb-8">
                <div class="bg-indigo-100 w-12 h-12 rounded-full flex items-center justify-center mr-4">
                    <span class="text-indigo-600 text-xl font-bold">2</span>
                </div>
                <h2 class="text-3xl font-bold text-gray-800">浮动垃圾的产生过程</h2>
            </div>
            
            <div class="content-card bg-white rounded-xl shadow-md p-8 mb-8">
                <p class="text-gray-700 mb-6">"浮动垃圾"是在 CMS 清理阶段由于垃圾收集与应用程序并发运行所产生的临时不可达对象。主要的形成机制如下：</p>
                
                <div class="grid md:grid-cols-3 gap-6 mb-8">
                    <div class="bg-indigo-50 rounded-lg p-5 text-center">
                        <div class="bg-indigo-100 w-16 h-16 rounded-full flex items-center justify-center mx-auto mb-4">
                            <i class="fas fa-clock text-indigo-600 text-2xl"></i>
                        </div>
                        <h4 class="font-bold text-gray-800 mb-2">时间窗口</h4>
                        <p class="text-gray-700 text-sm">在CMS的并发标记阶段之后到并发清除阶段期间，应用程序可能分配新对象</p>
                    </div>
                    
                    <div class="bg-indigo-50 rounded-lg p-5 text-center">
                        <div class="bg-indigo-100 w-16 h-16 rounded-full flex items-center justify-center mx-auto mb-4">
                            <i class="fas fa-exchange-alt text-indigo-600 text-2xl"></i>
                        </div>
                        <h4 class="font-bold text-gray-800 mb-2">状态变更</h4>
                        <p class="text-gray-700 text-sm">这些新对象在此期间可能变为不可达(被应用程序丢弃了所有引用)</p>
                    </div>
                    
                    <div class="bg-indigo-50 rounded-lg p-5 text-center">
                        <div class="bg-indigo-100 w-16 h-16 rounded-full flex items-center justify-center mx-auto mb-4">
                            <i class="fas fa-trash-alt text-indigo-600 text-2xl"></i>
                        </div>
                        <h4 class="font-bold text-gray-800 mb-2">未被回收</h4>
                        <p class="text-gray-700 text-sm">CMS在并发清除阶段认为这些对象是存活的，不会回收它们</p>
                    </div>
                </div>
                
                <p class="text-gray-700">CMS 并不将浮动垃圾视为真正的垃圾进行清除，这意味着这些对象占用的内存空间将会一直保留，直至下一次 CMS 垃圾收集。浮动垃圾的存在使得 CMS 无法完全回收所有无用对象，因此 CMS 需要预留一定空间(通常是堆内存的 20% 左右)以应对浮动垃圾的存在。</p>
            </div>
            
            <div class="content-card bg-white rounded-xl shadow-md overflow-hidden">
                <div class="md:flex">
                    <div class="md:w-2/3 p-8">
                        <h3 class="text-2xl font-bold text-gray-800 mb-4">浮动垃圾可视化</h3>
                        <p class="text-gray-700 mb-6">下图展示了在CMS垃圾收集过程中浮动垃圾的产生过程：</p>
                        <div class="mermaid">
                            graph LR
                                A[初始标记] --> B[并发标记]
                                B --> C[重新标记]
                                C --> D[并发清除]
                                D --> E[应用线程运行]
                                E -->|分配新对象| F[新对象]
                                F -->|丢弃引用| G[浮动垃圾]
                                style G fill:#f87171,stroke:#ef4444
                        </div>
                    </div>
                    <div class="md:w-1/3 bg-indigo-50 p-8 flex flex-col justify-center">
                        <div class="bg-white p-5 rounded-lg shadow-inner">
                            <h4 class="font-bold text-gray-800 mb-3">关键点说明</h4>
                            <ul class="text-gray-700 space-y-3">
                                <li class="flex items-start">
                                    <i class="fas fa-circle text-xs text-indigo-500 mr-2 mt-1.5"></i>
                                    <span>红色节点表示浮动垃圾的产生过程</span>
                                </li>
                                <li class="flex items-start">
                                    <i class="fas fa-circle text-xs text-indigo-500 mr-2 mt-1.5"></i>
                                    <span>箭头表示时间上的先后关系</span>
                                </li>
                                <li class="flex items-start">
                                    <i class="fas fa-circle text-xs text-indigo-500 mr-2 mt-1.5"></i>
                                    <span>并发阶段与应用线程同时运行</span>
                                </li>
                            </ul>
                        </div>
                    </div>
                </div>
            </div>
        </section>

        <!-- Section Divider -->
        <div class="section-divider"></div>

        <!-- Section 3 -->
        <section class="mb-16">
            <div class="flex items-center mb-8">
                <div class="bg-indigo-100 w-12 h-12 rounded-full flex items-center justify-center mr-4">
                    <span class="text-indigo-600 text-xl font-bold">3</span>
                </div>
                <h2 class="text-3xl font-bold text-gray-800">浮动垃圾的影响与应对策略</h2>
            </div>
            
            <div class="content-card bg-white rounded-xl shadow-md p-8 mb-8">
                <p class="text-gray-700 mb-6">浮动垃圾带来的影响主要体现在以下几方面：</p>
                
                <div class="grid md:grid-cols-3 gap-6 mb-8">
                    <div class="bg-white border border-gray-200 rounded-lg p-5 shadow-sm hover:border-indigo-300 transition-colors">
                        <div class="text-red-500 mb-3">
                            <i class="fas fa-memory text-2xl"></i>
                        </div>
                        <h4 class="font-bold text-gray-800 mb-2">内存浪费</h4>
                        <p class="text-gray-700 text-sm">浮动垃圾占据了堆内存的空间，使得真正可用的内存空间减少。内存空间的减少可能导致 CMS 更频繁地触发 GC，影响应用性能。</p>
                    </div>
                    
                    <div class="bg-white border border-gray-200 rounded-lg p-5 shadow-sm hover:border-indigo-300 transition-colors">
                        <div class="text-yellow-500 mb-3">
                            <i class="fas fa-tachometer-alt text-2xl"></i>
                        </div>
                        <h4 class="font-bold text-gray-800 mb-2">GC 频率提升</h4>
                        <p class="text-gray-700 text-sm">浮动垃圾占据了堆空间，CMS 需要更频繁地进行垃圾收集以释放空间，以避免应用出现内存不足的风险。这种频繁的 GC 操作可能会造成应用的吞吐量下降。</p>
                    </div>
                    
                    <div class="bg-white border border-gray-200 rounded-lg p-5 shadow-sm hover:border-indigo-300 transition-colors">
                        <div class="text-purple-500 mb-3">
                            <i class="fas fa-exclamation-triangle text-2xl"></i>
                        </div>
                        <h4 class="font-bold text-gray-800 mb-2">Full GC 增加</h4>
                        <p class="text-gray-700 text-sm">在内存压力较大或浮动垃圾增多的情况下，CMS 可能无法释放足够的空间，触发 Full GC 来完全回收内存。这种 Full GC 过程是单线程的，停顿时间较长，对系统性能影响较大。</p>
                    </div>
                </div>
            </div>
            
            <div class="content-card bg-white rounded-xl shadow-md p-8">
                <h3 class="text-2xl font-bold text-gray-800 mb-6">解决浮动垃圾的优化方法</h3>
                
                <div class="grid md:grid-cols-2 gap-6">
                    <div class="bg-indigo-50 rounded-lg p-6">
                        <h4 class="font-bold text-indigo-700 mb-4 flex items-center">
                            <i class="fas fa-arrow-up mr-2"></i>增大堆内存
                        </h4>
                        <p class="text-gray-700 mb-3">增大堆内存的容量，使得浮动垃圾对总内存的占比降低，从而减少 CMS 触发频率。</p>
                        <div class="bg-white p-3 rounded text-sm">
                            <code>-Xmx4g -Xms4g</code>
                        </div>
                    </div>
                    
                    <div class="bg-indigo-50 rounded-lg p-6">
                        <h4 class="font-bold text-indigo-700 mb-4 flex items-center">
                            <i class="fas fa-sliders-h mr-2"></i>调整CMS启动阈值
                        </h4>
                        <p class="text-gray-700 mb-3">通过降低 <code>CMSInitiatingOccupancyFraction</code> 的值来提前触发 CMS，避免浮动垃圾的积累带来内存压力。</p>
                        <div class="bg-white p-3 rounded text-sm">
                            <code>-XX:CMSInitiatingOccupancyFraction=60</code>
                        </div>
                    </div>
                    
                    <div class="bg-indigo-50 rounded-lg p-6">
                        <h4 class="font-bold text-indigo-700 mb-4 flex items-center">
                            <i class="fas fa-users mr-2"></i>调优CMS并发线程数
                        </h4>
                        <p class="text-gray-700 mb-3">适当增大 CMS 的并发线程数 (<code>CMSConcurrentMTEnabled</code>)，可以加快并发清除阶段的速度，减少浮动垃圾积累的时间。</p>
                        <div class="bg-white p-3 rounded text-sm">
                            <code>-XX:+CMSConcurrentMTEnabled -XX:ConcGCThreads=4</code>
                        </div>
                    </div>
                    
                    <div class="bg-indigo-50 rounded-lg p-6">
                        <h4 class="font-bold text-indigo-700 mb-4 flex items-center">
                            <i class="fas fa-exchange-alt mr-2"></i>使用G1 GC替代CMS
                        </h4>
                        <p class="text-gray-700 mb-3">对于浮动垃圾特别敏感的应用，使用 G1 GC 是一种解决方案。G1 GC 引入了分区回收机制，可以更高效地处理浮动垃圾。</p>
                        <div class="bg-white p-3 rounded text-sm">
                            <code>-XX:+UseG1GC</code>
                        </div>
                    </div>
                </div>
            </div>
        </section>

        <!-- Conclusion -->
        <section class="mb-16">
            <div class="content-card bg-gradient-to-r from-indigo-50 to-blue-50 rounded-xl shadow-md p-8">
                <h2 class="text-2xl font-bold text-gray-800 mb-6">总结</h2>
                <p class="text-gray-700 mb-6">浮动垃圾是 CMS 在并发清除阶段与应用程序并行运行带来的副作用。理解浮动垃圾的产生机制及其影响，有助于更有效地调优 CMS 及内存管理策略，以提高 JVM 的内存管理效率和应用的响应速度。</p>
                
                <div class="bg-white bg-opacity-70 rounded-lg p-5 border border-indigo-100">
                    <h3 class="font-bold text-indigo-700 mb-3 flex items-center">
                        <i class="fas fa-lightbulb mr-2"></i>实践建议
                    </h3>
                    <ol class="text-gray-700 space-y-2">
                        <li class="flex items-start">
                            <span class="bg-indigo-100 text-indigo-700 font-bold rounded-full w-6 h-6 flex items-center justify-center text-sm mr-3 flex-shrink-0">1</span>
                            <span>监控应用的GC日志，关注浮动垃圾的产生量</span>
                        </li>
                        <li class="flex items-start">
                            <span class="bg-indigo-100 text-indigo-700 font-bold rounded-full w-6 h-6 flex items-center justify-center text-sm mr-3 flex-shrink-0">2</span>
                            <span>根据应用特点调整CMS参数，找到最佳平衡点</span>
                        </li>
                        <li class="flex items-start">
                            <span class="bg-indigo-100 text-indigo-700 font-bold rounded-full w-6 h-6 flex items-center justify-center text-sm mr-3 flex-shrink-0">3</span>
                            <span>对于新项目，考虑使用G1 GC等更现代的垃圾收集器</span>
                        </li>
                    </ol>
                </div>
            </div>
        </section>
    </main>

    <!-- Footer -->
    <footer class="bg-gray-900 text-gray-300 py-8">
        <div class="max-w-5xl mx-auto px-4">
            <div class="flex flex-col md:flex-row justify-between items-center">
                <div class="mb-4 md:mb-0">
                    <h3 class="text-xl font-bold text-white mb-2">技术小馆</h3>
                    <p class="text-sm">分享前沿技术知识</p>
                </div>
                <div>
                    <a href="http://www.yuque.com/jtostring" class="text-indigo-300 hover:text-white transition-colors flex items-center">
                        <i class="fas fa-external-link-alt mr-2"></i>
                        <span>http://www.yuque.com/jtostring</span>
                    </a>
                </div>
            </div>
            <div class="border-t border-gray-700 mt-6 pt-6 text-sm text-center text-gray-500">
                &copy; 2023 技术小馆. 保留所有权利.
            </div>
        </div>
    </footer>

    <!-- Mermaid JS -->
    <script src="https://cdn.jsdelivr.net/npm/mermaid@latest/dist/mermaid.min.js"></script>
    <script>
        mermaid.initialize({
            startOnLoad: true,
            theme: 'default',
            flowchart: {
                useMaxWidth: false,
                htmlLabels: true,
                curve: 'basis'
            }
        });
    </script>
</body>
</html>
```